Guiding Vascular Access with the Sonic Flashlight - Preclinical Development and Validation

This dissertation concerns the development of a device called the Sonic Flashlight, which employs a novel method for viewing real-time ultrasound images inside the body exactly at the location where it is being scanned. While other augmented reality methods have previously been developed to view ultrasound and other medical imaging modalities within the body, they are generally much more complicated, slower and less robust than the Sonic Flashlight.In this dissertation, we aim to develop the Sonic Flashlight towards one particular clinical application, central vascular access, and lay the groundwork leading to the first clinical trials. The goal of central vascular access is to insert a catheter into a major vein to deliver medications in large quantities. These veins are usually not visible to the naked eye, so real-time ultrasound is employed to guide the needle into them. While real-time ultrasound guidance significantly enhances the safety of central venous access, learning this skill can be a challenge for the novice user, one major obstacle being the displaced sense of hand-eye coordination that occurs when the operator must look away from the operating field to view the conventional ultrasound monitor.We developed the 5th generation Sonic Flashlight, as well as a novel calibration method, called thin-gel calibration, as part of this dissertation. The thin-gel system allows us to accurately calibrate the Sonic Flashlight and measure the calibration accuracy. Finally, experiments were conducted with a variety of subject populations using vascular ultrasound phantoms and cadavers to validate Sonic Flashlight guidance, demonstrating that the device is ready for clinical trials

Robotic System Development for Precision MRI-Guided Needle-Based Interventions

This dissertation describes the development of a methodology for implementing robotic systems for interventional procedures under intraoperative Magnetic Resonance Imaging (MRI) guidance. MRI is an ideal imaging modality for surgical guidance of diagnostic and therapeutic procedures, thanks to its ability to perform high resolution, real-time, and high soft tissue contrast imaging without ionizing radiation. However, the strong magnetic field and sensitivity to radio frequency signals, as well as tightly confined scanner bore render great challenges to developing robotic systems within MRI environment. Discussed are potential solutions to address engineering topics related to development of MRI-compatible electro-mechanical systems and modeling of steerable needle interventions. A robotic framework is developed based on a modular design approach, supporting varying MRI-guided interventional procedures, with stereotactic neurosurgery and prostate cancer therapy as two driving exemplary applications. A piezoelectrically actuated electro-mechanical system is designed to provide precise needle placement in the bore of the scanner under interactive MRI-guidance, while overcoming the challenges inherent to MRI-guided procedures. This work presents the development of the robotic system in the aspects of requirements definition, clinical work flow development, mechanism optimization, control system design and experimental evaluation. A steerable needle is beneficial for interventional procedures with its capability to produce curved path, avoiding anatomical obstacles or compensating for needle placement errors. Two kinds of steerable needles are discussed, i.e. asymmetric-tip needle and concentric-tube cannula. A novel Gaussian-based ContinUous Rotation and Variable-curvature (CURV) model is proposed to steer asymmetric-tip needle, which enables variable curvature of the needle trajectory with independent control of needle rotation and insertion. While concentric-tube cannula is suitable for clinical applications where a curved trajectory is needed without relying on tissue interaction force. This dissertation addresses fundamental challenges in developing and deploying MRI-compatible robotic systems, and enables the technologies for MRI-guided needle-based interventions. This study applied and evaluated these techniques to a system for prostate biopsy that is currently in clinical trials, developed a neurosurgery robot prototype for interstitial thermal therapy of brain cancer under MRI guidance, and demonstrated needle steering using both asymmetric tip and pre-bent concentric-tube cannula approaches on a testbed